Chemical mechanical polishing apparatus

ABSTRACT

A “black belt” phenomenon that may be caused by an eddy of a slurry may be prevented when a wafer is polished by a chemical mechanical polishing (CMP) apparatus that includes a polishing pad to be supplied with the slurry, a polishing head including a top ring adapted to hold a wafer, and a buffer ring forming a buffer space between an edge region of the wafer and an eddy region of the slurry that may be formed in front of the polishing head.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2004-0111050 filed in the Korean Intellectual Property Office on Dec. 23, 2004, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a chemical mechanical polishing (CMP) apparatus, and more particularly to a chemical mechanical polishing apparatus for polishing a surface of a wafer using mechanical friction as well as a chemical polishing agent.

(b) Description of the Related Art

Recently, as design rules of semiconductor devices have been reduced, line widths of wires have also been getting smaller. Therefore, a dual damascene process has been developed to form wires with the use of copper which has low resistance (Rs).

According to the dual damascene process, a via and a metal line are typically formed in the following process. That is, a dual damascene pattern is firstly formed by etching an insulating layer on a semiconductor substrate according to a via-first or trench-first scheme. A conductive material such as copper, etc., is then filled in the dual damascene pattern. Next, the via and the metal line are finalized by removing a portion of the conductive material outside the via and trench using a chemical mechanical polishing (referred to as “CMP” below) process.

The CMP process is a process for polishing a surface of a wafer coated with tungsten, an oxide, etc., by using mechanical friction as well as a chemical polishing agent. Mechanical polishing is a process for polishing a surface of a wafer using friction between a polishing pad and the surface of the wafer by rotating the wafer when it is fixed on a rotating polishing head, with the wafer pressed against the polishing pad. In addition, chemical polishing is a process used to polish a surface of a wafer using a slurry supplied between a polishing pad and the wafer as a chemical polishing agent.

According to such a CMP process, excellent planarity may be obtained in wide regions (e.g., regions where device features may be relatively widely spaced apart) as well as narrow regions (e.g., regions where device features may be relatively close together). Accordingly, the CMP process is particularly adapted to the trend toward increasing wafer diameter.

Hereinafter, a conventional CMP apparatus will be described in detail with reference to FIG. 1.

As shown in FIG. 1, a conventional CMP apparatus for performing the CMP process includes a polishing pad 102 which is rotating or fixed, and a polishing head 104 which has a top ring 104a used for fixedly holding a wafer W. In addition, a slurry supply nozzle (not shown) is installed in an upper part of the polishing pad 102 in order to supply a slurry 106 to the polishing pad 102.

When a copper layer filling a dual damascene pattern formed on a wafer is planarized by such a CMP apparatus, the polishing head 104 effectively polishes the wafer W by pressing the wafer W against the polishing pad while the slurry is supplied to the polishing pad 102 through the supply nozzle.

However, according to the CMP apparatus, when a wafer W is polished as the polishing head 104 proceeds in the arrow direction, the slurry 106 is accumulated in front of the wafer W because the slurry 106 is pushed by the wafer W toward the moving direction of the polishing head 104. Therefore in this case, the amount of the slurry 106 is locally increased.

When the amount of the slurry 106 is locally increased, an eddy of the slurry is created in front of the wafer W by the rotational and translational movements of the wafer W. In this case, the wafer W makes more contact with the slurry 106, and accordingly, the copper layer around an edge of the wafer W may become “dented” (e.g., locally overpolished, or removed to a greater degree, around the wafer edge) by a chemical reaction of the slurry 106.

Therefore, a process defect, such as a “black belt,” can be generated in the edge bead removal (EBR) zone of the wafer W when the CMP process is finished, and such defect may result in a short-circuit of the copper wiring thereby deteriorating a yield of a device.

The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form prior art or other information that is already known in this or any other country to a person of ordinary skill in the art.

SUMMARY OF THE INVENTION

The present invention has been made in an effort to provide a CMP apparatus having advantages of reducing and/or preventing a “black belt” phenomenon caused by an eddy (or local accumulation) of a CMP slurry.

An exemplary CMP apparatus according to an embodiment of the present invention includes a polishing pad (adapted to be supplied with a slurry), a polishing head including a top ring for holding a wafer, and a buffer ring providing a buffer space around a wafer edge region (e.g., between an edge region of the wafer and a slurry eddy that may be formed in front of the polishing head).

The buffer ring may be fixedly installed on or attached to the top ring or be integrally formed therewith, and the buffer ring may have a radius that is about 0.1-5 mm larger than that of the top ring.

Even though a slurry on a polishing pad may create an eddy in front of the moving direction of a polishing head, such a CMP apparatus can prevent the phenomenon in which a copper layer around an edge of the wafer W may become dented (or locally overpolished) by a chemical reaction of the slurry with material at or near the wafer edge because of the 0.1-5 mm-sized buffer space around the wafer edge (e.g., formed between a slurry eddy and the edge region of the wafer).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional (or schematic) diagram of a conventional CMP apparatus.

FIG. 2 is a cross-sectional (or schematic) diagram of a CMP apparatus according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings.

FIG. 2 is a diagram of a CMP apparatus according to an exemplary embodiment of the present invention.

As shown in FIG. 2, a CMP apparatus of the present embodiment includes a polishing pad 12 and a polishing head 14. Although not shown in FIG. 2, the polishing pad 12 may be installed on or attached or fixed to an upper surface of a platen that is rotatably or fixedly supported by a supporting shaft.

The polishing head 14 includes a top ring 14a used for holding the wafer W. In addition, a slurry supply nozzle (not shown) is installed above or at an upper part of the polishing pad 12 in order to supply the slurry 16 to the polishing pad 12. Therefore, when the slurry 16 is supplied to the polishing pad 12 through the slurry supply nozzle, the polishing head 14 polishes the wafer W by pressing the wafer W against the polishing pad 12.

In the present CMP apparatus, a buffer ring 14b may be installed on, around or at the top ring 14 a of the polishing head 14. The buffer ring 14 b may be configured to include a buffer space 14′b thereunder, which may have a predetermined size (e.g., width or annular radius) such that the slurry that may accumulate in front of the moving direction (shown by an arrow) of the polishing head 14 may be inhibited or prevented from contacting an edge region of the wafer W. Although FIG. 2 illustrates that the buffer ring 14 b and the top ring 14 a are formed as separate members, the buffer ring 14 b and the top ring 14 a may be integrally formed (e.g., they may comprise an integral unit).

Furthermore, the buffer ring 14 b may be configured without a buffer space, in which case the buffer ring 14 b may have a predetermined size (e.g., width or annular radius) of 0.1-5.0 mm, 0.2-3.0 mm, or any range of values therein. Providing a buffer space 14′b adjacent to the wafer edge, however, may reduce trapping of slurry particles against the edge of the wafer W (e.g., between the wafer edge and the inner surface of buffer ring 14 b), and thus reduce potential damage to the wafer W and/or improve device yield.

Buffer space 14′b and/or the buffer ring 14 b may have a radius of about 0.1-5 mm greater than the top ring. According to such a configuration, the buffer space 14′b of the above-mentioned size, for example 0.1-5 mm, may be provided between an interior lateral side of the buffer ring 14 b and the edge of the wafer W. Buffer ring 14 b and/or buffer space 14′b may be formed according to techniques known to those skilled in the art (e.g., machining).

In accordance with the present CMP apparatus, the slurry 16 on the polishing pad 12 may accumulate at the exterior front of the buffer ring 14 b in the moving direction of the polishing head 14. Therefore, even though the slurry eddy may accumulate in front of the moving direction of the polishing head 14, the “black belt” or “denting” phenomenon involving a copper layer at or around a wafer edge and/or bead region can be reduced or prevented because of the 0.1-5 mm-sized buffer space 14′b around the periphery of the polishing head 14 (e.g., formed between the eddy region of the slurry and the edge region of the wafer).

As described above, according to an exemplary embodiment of the present CMP apparatus, a buffer ring may provide or form a buffer space around the periphery or circumference of the polishing head (e.g., to provide a buffer between the edge region of the wafer and a slurry eddy that may be formed in front of the polishing head in its direction of movement). Therefore, the present CMP apparatus can reduce or prevent the phenomenon that a copper layer is dented by the slurry eddy, a so-called “black belt” phenomenon. As a result, device yield may be enhanced because a short circuit or disconnection in a copper line due to the dent or black belt phenomenon may be reduced or prevented.

While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 

1. An apparatus for chemical mechanical polishing, comprising: a polishing pad to be supplied with a slurry; a polishing head including a top ring adapted to hold a wafer; and a buffer ring including a buffer space between an edge region of the wafer and an eddy region of the slurry formed in front of the polishing head.
 2. The apparatus of claim 1, wherein the buffer ring is fixed to the top ring or, together with the top ring, comprise an integral unit.
 3. The apparatus of claim 1, wherein the buffer ring has a radius of about 0.1-5 mm greater than the top ring.
 4. The apparatus of claim 2, wherein the buffer ring has a radius of about 0.1-5 mm greater than the top ring.
 5. An chemical mechanical polishing apparatus, comprising: a polishing pad; a polishing head including a top ring adapted to hold a wafer; and a buffer ring around the polishing head.
 6. The apparatus of claim 5, wherein the buffer ring further comprises a buffer space.
 7. The apparatus of claim 5, wherein the buffer ring is fixed to the top ring.
 8. The apparatus of claim 5, wherein the buffer ring and the top ring comprise an integral unit.
 9. The apparatus of claim 5, wherein the buffer ring has an annular radius of about 0.1-5 mm.
 10. The apparatus of claim 6, wherein the buffer ring has an annular radius of about 0.1-5 mm.
 11. The apparatus of claim 6, wherein the buffer space has an annular radius of about 0.1-5 mm.
 12. The apparatus of claim 5, further comprising a slurry nozzle configured to supply slurry to the polishing pad.
 13. A method of chemical mechanical polishing, comprising: polishing a wafer by pressing the wafer against a polishing pad using a polishing head including a top ring adapted to hold the wafer; and reducing or preventing damage to an edge region of the wafer from an eddy of the slurry, using a buffer ring around the polishing head.
 14. The method of claim 13, wherein the buffer ring is fixed to the top ring.
 15. The method of claim 13, wherein the buffer ring and the top ring comprise an integral unit.
 16. The method of claim 13, wherein the buffer ring has an annular radius of about 0.1-5 mm.
 17. The method of claim 13, wherein the buffer ring further comprises a buffer space.
 18. The method of claim 17, wherein the buffer space has an annular radius of about 0.1-5 mm.
 19. The method of claim 13, further comprising supplying a slurry to the polishing pad. 